Organic light emitting diode display device and method of fabricating the same

ABSTRACT

An organic light emitting diode display device includes a first substrate including a display region, wherein a plurality of pixel regions are defined in the display region; a first electrode over the first substrate and in each of the plurality of pixel regions; a first bank on edges of the first electrode and including an insulating material blocking penetration of light; a second bank on the first bank and including an insulating material having a hydrophobic property; an organic light emitting layer on the first electrode and a portion of the first bank; and a second electrode on the organic light emitting layer and covering an entire surface of the display region.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a reissue of U.S. Pat. No. 9,123,675, whichissued Sep. 1, 2015 from U.S. patent application Ser. No. 14/098,098,filed Dec. 5, 2013, and claims the benefit of Korean Patent ApplicationNo. 10-2013-0075522 filed in Korea on Jun. 28, 2013, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an organic light emitting diode (OLED) displaydevice, which may be referred to as an organic electroluminescentdisplay device. More particularly, the invention to an OLED displaydevice having a bank of a double-layered structure and a method offabricating the same.

2. Discussion of the Related Art

An OLED display device of flat panel display devices has high brightnessand low driving voltage. The OLED display device is a self-emitting typeand has excellent characteristics of view angle, contrast ratio,response time, etc.

Accordingly, the OLED display device is widely used for a television, amonitor, a mobile phone, and so on.

The OLED display device includes an array element and an organic lightemitting diode. The array element includes a switching thin filmtransistor (TFT), which is connected to a gate line and a data line, adriving TFT, which is connected to the switching TFT, and a power line,which is connected to the driving TFT. The organic light emitting diodeincludes a first electrode, which is connected to the driving TFT, andfurther includes an organic light emitting layer and a second electrode.

In the OLED display device, light from the organic light emitting layerpasses through the first electrode or the second electrode to display animage. A top emission type OLED display device, where the light passesthrough the second electrode, has an advantage in an aperture ratio.

Generally, the organic light emitting layer is formed by a thermaldeposition method using a shadow mask. However, the shadow mask sagsbecause the shadow mask becomes larger with an increase in sizes ofdisplay devices. As a result, there is a problem in depositionuniformity in the larger display device. In addition, since a shadoweffect is generated in the thermal deposition method using the shadowmask, it is very difficult to fabricate a high resolution OLED displaydevice, e.g., above 250 PPI (pixels per inch).

Accordingly, a method different from the thermal deposition method usingthe shadow mask has been introduced.

In the method, a liquid phase organic light emitting material is sprayedor dropped in a region surrounded by a wall using an liquid-releasingapparatus or a nozzle-coating apparatus and cured to form the organiclight emitting layer.

FIGS. 1A to 1C are schematic cross-sectional views showing an OLEDdisplay device according to the related art in steps of fabricating theOLED display device and steps of forming a bank and forming an organiclight emitting layer by spraying or dropping a liquid phase organiclight emitting material.

To spray or drop the liquid phase organic light emitting material by theliquid-releasing apparatus or the nozzle-coating apparatus, the bank,which is formed on a first electrode and surrounds a pixel region, isrequired to prevent the liquid phase organic light emitting materialfrom flooding into a next pixel region. Accordingly, the bank is formedon edges of the first electrode before forming the organic lightemitting layer.

At this time, the bank is formed of a material having a hydrophobicproperty. The hydrophobic bank prevents the liquid phase organic lightemitting material, which has a hydrophilic property, from being formedon the bank and flooding into the next pixel region due to amis-alignment of the liquid-releasing apparatus or the nozzle-coatingapparatus or an excessive amount of the organic light emitting material.

As shown in FIG. 1A, the bank may be formed by a mask process, whichincludes a light-exposing step using an exposing mask 91 and adeveloping step after an organic insulating material having ahydrophobic property is applied to an entire surface of a substrate 10on which a first electrode 50 is formed at each pixel region P.

Here, the light-exposing step using the exposing mask 91 may includeirradiating high lux UV light of several hundred mW/cm².

With an increase in a size of a display device, a substrate for thedisplay device has been larger, and a scan-type exposure has beenperformed onto the large-sized substrate because it is not possible toexpose a whole of the large-sized substrate to light at a time.

The scan-type exposure decreases the productivity per unit time ascompared to a process of exposing the substrate to light at a time. Toprevent the productivity from being decreased, in the scan-typeexposure, high lux UV light of several hundred mW/cm² instead of typicalUV light of several dozen mW/cm², which is generally used in alight-exposing step, has been used.

When the light-exposing step with the high lux UV light is performed, ascan speed is several times to several dozen times as fast as thetypical UV light. Therefore, a process time of the light-exposing stepper unit time decreases, and the productivity per unit time increases.

However, when the high lux UV light of several hundred mW/cm² isirradiated to an organic insulating material layer 52 by a scan-typeexposure apparatus 80 using the high lux UV light, light from thescan-type exposure apparatus 80 may be reflected by signal lines 30 orelectrodes (not shown) of a metallic material or by a stage 93 of theexposure apparatus 80 and may reach a central portion of the pixelregion P even if an amount of the light is a little. Here, the organicinsulating material layer 52 has a hydrophobic property.

Accordingly, as shown in FIG. 1B, after developing the organicinsulating material layer 52 of FIG. 1A exposed to light, the bank 53 isformed along boundaries of the pixel region P, and organic insulatingmaterial residues 54 with the hydrophobic property remain on the firstelectrode 50 at the central portion of the pixel region P. The organicinsulating material residues 54 may be referred to as organic insulatingmaterial residual layers.

Meanwhile, the bank 53 has a width w1′ larger than a designated width w1because a tail is lengthened due to the reflected light during thelight-exposing step.

Next, as shown in FIG. 1C, by spraying or dropping a liquid phaseorganic light emitting material from an liquid-releasing apparatus 95into the pixel region P, which is surrounded by the bank 53, the pixelregion P is filled with the organic light emitting material. The organiclight emitting material is dried and cured by heat to form an organiclight emitting layer 55.

However, since the residues 54 have the hydrophobic property, theresidues 54 hinder the liquid phase organic light emitting material frombeing spread in the pixel region P when the liquid phase organic lightemitting material is sprayed or dropped. Accordingly, as shown in FIG.1C and FIG. 2, which is a picture of showing one pixel region in therelated art OLED display device, the organic light emitting layer 55 isnot formed around the hydrophobic bank 53, or a portion of the organiclight emitting layer around the hydrophobic bank 53 has a thinnerthickness than portions in other regions. Thus, dark images aredisplayed in edges of the pixel region P. In addition, the OLED displaydevice is degraded fast due to the difference in thicknesses, and thelifetime of the OLED display device is shortened.

Moreover, as stated above, since the bank 53 has the width w1′ largerthan the designed width w1, an area for the organic light emitting layer55 is reduced, and the aperture ratio is lowered.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an OLED display devicethat substantially obviates one or more of the problems due tolimitations and disadvantages of the related art.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. These andother advantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

In accordance with the present invention, as embodied and broadlydescribed herein, an organic light emitting diode display deviceincludes a first substrate including a display region, wherein aplurality of pixel regions are defined in the display region; a firstelectrode over the first substrate and in each of the plurality of pixelregions; a first bank on edges of the first electrode and including aninsulating material blocking penetration of light; a second bank on thefirst bank and including an insulating material having a hydrophobicproperty; an organic light emitting layer on the first electrode and aportion of the first bank; and a second electrode on the organic lightemitting layer and covering an entire surface of the display region.

In another aspect, a method of fabricating an organic light emittingdiode display device includes forming a first electrode over a firstsubstrate including a display region, which includes a plurality ofpixel regions, the first electrode formed in each of the plurality ofpixel regions; forming a first bank on edges of the first electrode andthe first bank including an insulating material blocking penetration oflight and having a first width; forming a second bank on the first bankand the second bank including an insulating material having ahydrophobic property and having a second width smaller than the firstwidth; forming an organic light emitting layer on the first electrodeand a portion of the first bank surrounded by the second bank in each ofthe plurality of pixel regions; and forming a second electrode on theorganic light emitting layer, the second electrode covering an entiresurface of the display region.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIGS. 1A to 1C are schematic cross-sectional views showing an OLEDdisplay device according to the related art in steps of fabricating theOLED display device.

FIG. 2 is a picture showing one pixel region in the related art OLEDdisplay device.

FIG. 3 is a circuit diagram of one pixel region of an OLED displaydevice.

FIG. 4 is a schematic cross-sectional view of an OLED display deviceaccording to an embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of an OLED display deviceaccording to another embodiment of the present invention.

FIG. 6 is a schematic crass-sectional view of an OLED display deviceaccording to another embodiment of the present invention.

FIG. 7 is a picture showing one pixel region in an OLED display deviceaccording to the present invention when the OLED display device isdriven.

FIGS. 8A to 8H are cross-sectional views showing a fabricating processof an OLED display device according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments,examples of which are illustrated in the accompanying drawings.

FIG. 3 is a circuit diagram of one pixel region of an OLED device.

As shown in FIG. 3, an OLED display device includes a switching thinfilm transistor (TFT) STr, a driving TFT DTr, a storage capacitor StgCand an light emitting diode E in each pixel region P.

On a substrate (not shown), a gate line GL along a first direction and adata line DL along a second direction are formed. The gate line GL andthe data line DL cross each other to define the pixel region P. A powerline PL for providing a source voltage to the emitting diode E is formedto be parallel to and spaced apart from the data line DL.

The switching TFT STr is connected to the gate and data lines GL and DL,and the driving TFT DTr and the storage capacitor StgC are connected tothe switching TFT STr and the power line PL. The light emitting diode Eis connected to the driving TFT DTr.

A first electrode of the light emitting diode E is connected to a drainelectrode of the driving TFT DTr, and a second electrode of the lightemitting diode E is grounded.

When the switching TFT STr is turned on by a gate signal applied throughthe gate line GL, a data signal from the data line DL is applied to thegate electrode of the driving TFT DTr and an electrode of the storagecapacitor StgC. When the driving TFT DTr is turned on by the datasignal, an electric current is supplied to the light emitting diode Efrom the power line PL. As a result, the light emitting diode E emitslight. In this case, when the driving TFT DTr is turned on, a level ofan electric current applied from the power line PL to the light emittingdiode E is determined such that the light emitting diode E can produce agray scale. The storage capacitor StgC serves to maintain the voltage ofthe gate electrode of the driving TFT DTr when the switching TFT STr isturned off. Accordingly, even if the switching TFT STr is turned off, alevel of an electric current applied from the power line PL to the lightemitting diode E is maintained until a next frame.

FIG. 4 is a schematic cross-sectional view of an OLED display deviceaccording to an embodiment of the present invention. For convenience ofexplanation, a driving area where a driving TFT DTr is formed, a pixelregion P where an light emitting diode E is formed, and a switching area(not shown) where a switching TFT (not shown) is formed are defined.

As shown in FIG. 4, an OLED display device 101 of the present inventionincludes a first substrate 110, where the driving TFT DTr, the switchingTFT (not shown) and the light emitting diode E are formed, and a secondsubstrate 170 for encapsulation. The second substrate 170 may be aninorganic insulating film or an organic insulating film.

A gate line (not shown) and a data line 130 are formed on the firstsubstrate 110. The gate line and the data line 130 cross each other todefine the pixel region P. A power line (not shown) for providing avoltage to the light emitting diode E is formed to be parallel to andspaced apart from the data line 130.

In each pixel region P, the switching TFT is connected to the gate lineand the data line 130, and the driving TFT DTr and a storage capacitorare connected to the switching TFT and the power line.

The driving TFT DTr includes a gate electrode 115, a gate insulatinglayer 118, an oxide semiconductor layer 120, an etch-stopper 122, asource electrode 133 and a drain electrode 136. The gate insulatinglayer 118 covers the gate electrode 115, and the oxide semiconductorlayer 120 is disposed on the gate insulating layer 118. The oxidesemiconductor layer 120 corresponds to the gate electrode 115. Theetch-stopper 122 covers a center of the oxide semiconductor layer 120.The source electrode 133 and the drain electrode 136 are formed on theetch-stopper 122 and spaced apart from each other. The source electrode133 and the drain electrode 136 contact both ends of the oxidesemiconductor layer 120, respectively. Although not shown, the switchingTFT has substantially the same structure as the driving TFT DTr.

In FIG. 4, each of the driving TFT DTr and the switching TFT includesthe oxide semiconductor layer 120 of an oxide semiconductor material.Alternatively, as shown in FIG. 5, each of the driving TFT DTr and theswitching TFT may include a gate electrode 213, a gate insulating layer218, a semiconductor layer 220 including an active layer 220a ofintrinsic amorphous silicon and an ohmic contact layer 220b ofimpurity-doped amorphous silicon, a source electrode 233 and a drainelectrode 236. In FIGS. 4 and 5, the driving TFT DTr has a bottom gatestructure where the gate electrode 115 or 213 is positioned at a lowestlayer.

Meanwhile, in an alternate embodiment each of the driving TFT DTr andthe switching TFT may have a top gate structure where the semiconductorlayer is positioned at a lowest layer. Specifically, as shown in FIG. 6,each of the driving TFT DTr and the switching TFT may include asemiconductor layer 313, which includes an active region 313a ofintrinsic polysilicon and impurity-doped regions 313b at both sides ofthe active region 313a, on a first substrate 310, a gate insulatinglayer 316, a gate electrode 320 corresponding to the active region 313aof the semiconductor layer 313, an interlayer insulating layer 323having semiconductor contact holes 325, which expose the impurity-dopedregions 313b of the semiconductor layer 313, and source and drainelectrodes 333 and 336 respectively connected to the impurity-dopedregions 313b through the semiconductor contact holes 325.

The top gate structure TFT requires the interlayer insulating layer 323in comparison to the bottom gate structure TFT. In the top gatestructure TFT, the gate line (not shown) is formed on the gateinsulating layer 316, and the data line (not shown) is formed on theinterlayer insulating layer 323.

Referring again to FIG. 4, a passivation layer 140, which includes adrain contact hole 143 exposing the drain electrode 136 of the drivingTFT DTr, is formed over the driving TFT DTr and the switching TFT. Forexample, the passivation layer 140 may be formed of an organicinsulating material, e.g., photo-acryl, to have a flat top surface.

A first electrode 150, which contacts the drain electrode 136 of thedriving TFT DTr through the drain contact hole 143, is formed on thepassivation layer 140 and separately in each pixel region P.

The first electrode 150 is formed of a conductive material having arelatively high work function, e.g., about 4.8 eV to 5.2 eV. Forexample, the first electrode 150 may be formed of a transparentconductive material such as indium-tin-oxide (ITO) to serve as an anode.

A bank 153 having a double-layered structure, which includes a firstbank 153a and a second bank 153b, is formed on the first electrode 150along boundaries of the pixel region P. The bank 153 overlaps edges ofthe first electrode 150 such that a center of the first electrode 150 isexposed by the bank 153.

The first bank 153a, as a lower layer, may be formed of an insulatingmaterial having relatively high light absorptivity and blockingpenetration of light such as chromium oxide (CrOx), for example. Thefirst bank 153a has a first width. The second bank 153b is disposed onthe first bank 153a and has a second width w′ smaller than the firstwidth. The second bank 153b may be formed of an organic material havinga hydrophobic property. The organic material may include at 35 least oneof polyimide containing fluorine (F), styrene, methylmethacrylate, andpolytetrafluoroethylene.

In the OLED display device 101 including the bank 153 of adouble-layered structure, which includes the first bank 153a blockingpenetration of light and having the first width and the second bank 153bhaving the hydrophobic property and the second width w′, hydrophobicresidues hardly remain on the first electrode 150 after forming the bank153 because light is not reflected by signal lines of a metallicmaterial such as the gate line, the data line 130, and the power lineunder the first bank 153a or a stage of an exposure apparatus when thesecond bank 153b is formed by performing an exposing step using ascan-type exposure apparatus with high lux UV light.

Accordingly, a liquid phase organic light emitting material can bespread well in the pixel region P surrounded by the bank 153 when thematerial is sprayed or dropped.

Furthermore, since the second bank 153b has the second width w′ smallerthan the first width of the first bank 153a and the second width w′corresponds to a designed width w, which includes an error rangeconsidering a practical exposing process, the aperture ratio of the OLEDdisplay device of the invention is improved as compared to the relatedart OLED display device including the bank 53 of FIG. 1C having thelarge tails.

A method of forming the bank 153 will be described in more detail later.

An organic light emitting layer 155 is formed in each pixel region Psurrounded by the bank 153 having the double-layered structure. Theorganic light emitting layer 155 includes red, green and blue lightemitting materials in respective pixel regions P.

The organic light emitting layer 155 is formed by forming an organiclight emitting material layer and curing the organic light emittingmaterial layer. The organic light emitting material layer is formed bycoating, i.e., spraying or dropping a liquid phase organic lightemitting material by an liquid-releasing apparatus or a nozzle-coatingapparatus.

Referring to FIG. 4 and FIG. 7, which is a picture showing one pixelregion in an OLED display device according to the present invention whenthe OLED display device is driven, in the OLED display device 101including the bank 153 having a double-layered structure, the organiclight emitting layer 155 is formed to have a uniform thickness in anentire surface of an area surrounded by the bank 153 at each pixelregion P. Substantially, the organic light emitting layer 155 has auniform thickness in an area surrounded by the first bank 153a.

This is why the liquid phase organic light emitting material is spreadwell because there is no hydrophobic residue on the first electrode 150.

FIG. 4 shows a single-layered organic light emitting layer 155.Alternatively, to improve light emission efficiency, the organic lightemitting layer 155 may have a multi-layered structure. For example, theorganic light emitting layer 155 may include a hole injecting layer, ahole transporting layer, a light emitting material layer, an electrontransporting layer and an electron injecting layer stacked on the firstelectrode 150 as an anode. The organic light emitting layer 155 may be aquadruple-layered structure of a hole transporting layer, alight-emitting material layer, an electron transporting layer and anelectron injecting layer or a triple-layered structure of a holetransporting layer, a light emitting material layer and an electrontransporting layer.

A second electrode 160 is formed on the organic light emitting layer 155and covers an entire surface of a display region of the first substrate110. The second electrode 160 is formed of a metallic material having arelatively low work function, e.g., aluminum (Al), Al alloy such asaluminum neodymium (AlNd), silver (Ag), magnesium (Mg), gold (Au), oraluminum magnesium alloy (AlMg). The second electrode 160 serves as acathode.

The first electrode 150, the organic light emitting layer 155 and thesecond electrode 160 constitute the light emitting diode E.

A seal pattern (not shown) of a sealant or a fit material is formed onedges of the first substrate 110 or the second substrate 170. The firstand second substrates 110 and 170 are attached using the seal pattern. Aspace between the first and second substrates 110 and 170 has a vacuumcondition or an inert gas condition. The second substrate 170 may be aflexible plastic substrate or a glass substrate.

Alternatively, the second substrate 170 may be a film contacting thesecond electrode 160. In this instance, the film-type second substrateis attached to the second electrode 160 by an adhesive layer.

In addition, an organic insulating film or an inorganic insulating filmmay be formed on the second electrode 160 as a capping layer. In thisinstance, the organic insulating film or the inorganic insulating filmserves as the encapsulation film without the second substrate 170.

Hereinafter, a method of fabricating the OLED display device isexplained with reference to drawings. FIGS. 8A to 8H are cross-sectionalviews showing a fabricating process of an OLED display device accordingto an embodiment of the present invention. The explanation is focused ona bank having a double-layered structure.

As shown in FIG. 8A, the gate line (not shown), the data line 130 andthe power line (not shown) are formed on the first substrate 110. Inaddition, the switching TFT (not shown) connected to the gate line andthe data line 130 and the driving TFT DTr connected to the switching TFTand the power line are formed in the switching area (not shown) and inthe driving area, respectively.

As explained above, each of the switching TFT and the driving TFT DTrhas a bottom gate type TFT including the gate electrode 115 of FIG. 4 or213 of FIG. 5 as a lowest layer or a top gate type TFT including thesemiconductor layer 313 of FIG. 6 as a lowest layer. The bottom gatetype TFT includes the oxide semiconductor layer 120 of FIG. 4 or theamorphous silicon semiconductor layer 220 of FIG. 5 including the activelayer 220a and the ohmic contact layer 220b, and the top gate type TFTincludes the poly-silicon semiconductor layer 313 of FIG. 6.

Here, the switching TFT and the driving TFT DTr may be the bottom gatetype TFT including an oxide semiconductor layer. Therefore, the gateelectrode 115 of the driving TFT DTr is formed on the first substrate110, the gate insulating layer 118 is formed on the gate electrode 115,and the oxide semiconductor layer 120 is formed on the gate insulatinglayer 118 corresponding to the gate electrode 115. The etch-stopper 122is formed on the oxide semiconductor layer 120 and covers the center ofthe oxide semiconductor layer 120. The source and drain electrodes 133and 136 are formed on the etch-stopper 122 and spaced apart from eachother.

Next, an organic insulating material, e.g., photo-acryl, is coated overthe switching TFT and the driving TFT DTr and is patterned to form thepassivation layer 140 having a flat top surface and including the draincontact hole 143. The drain electrode 136 of the driving TFT DTr isexposed through the drain contact hole 143.

Next, a transparent conductive material, which has a relatively highwork function, is deposited on the passivation layer 140 and patternedto form the first electrode 150. The first electrode 150 contacts thedrain electrode 136 of the driving TFT DTr through the drain contacthole 143 and is separated in each pixel region P. For example, thetransparent conductive material may be indium tin oxide (ITO).

Next, as shown in FIG. 8B, an inorganic insulating material havingrelatively high light absorptivity and blocking penetration of light,e.g., chromium oxide (CrOx) is deposited on the first electrode 150 andthe passivation layer 140 and is patterned to thereby form the firstbank 153a. The first bank 153a corresponds to the boundaries of thepixel region P and overlaps the edges of the first electrode 150. Thefirst bank 153a has the first width.

As shown in FIG. 8C, an organic insulating material layer 152 is formedon the first bank 153 and the first electrode 150. For example, theorganic insulating material layer 152 may be formed by applying anorganic insulating material to a substantially entire surface of thefirst substrate 110. The organic insulating material, beneficially, mayhave a photosensitive property and a hydrophobic property. The organicinsulating material may include at least one of polyimide containingfluorine (F), styrene, methylmethacrylate, and polytetrafluoroethylene.

An exposing mask 191 including a light-transmitting region TA and alight-blocking region BA is disposed over the organic insulatingmaterial layer 152, and a scan-type exposure apparatus 195 includinghigh lux UV light of 100 to 990 mW/cm² is disposed over the exposingmask 191. The organic insulating material layer 152 is scanned by thescan-type exposure apparatus 195 by selectively irradiating the high luxUV light to the organic insulating material layer 152, therebyperforming a light-exposing process.

A portion of the organic insulating material layer 152 corresponding tothe light-transmitting region TA of the exposing mask 191 is exposed tothe UV light, and a portion of the organic insulating material layer 152corresponding to the light-blocking region BA is not exposed to the UVlight. Here, the organic insulating material layer 152 is shown to havea negative type photosensitive property with which an exposed portion ofthe organic insulating material layer 152 remains after a developingprocess. Alternatively, the organic insulating material layer 152 mayhave a positive type photosensitive property, and at this time, thepositions of the light-transmitting region TA and the light-blockingregion BA are exchanged.

At this time, the high lux UV light reaching the organic insulatingmaterial layer 152 through the light-transmitting region TA of theexposing mask 191 passes through the organic insulating material layer152 and heads toward elements under the organic insulating materiallayer 152. However, the UV light is blocked by the first bank 153a,which is formed of an insulating material having relatively high lightabsorptivity and blocking penetration of light, and the UV light passingthrough the organic insulating material layer 152 is prevented frombeing incident on elements under the first bank 153a.

More particularly, the first bank 153a may have the same shape as thelight-transmitting region TA of the exposing mask 191 for forming thesecond bank 153b of FIG. 8D, and the first bank 153a may have the firstwidth larger than the second width of the second bank 153b of FIG. 8D.The light-transmitting region TA may have substantially the same widthas the second width of the second bank 153b of FIG. 8D.

Therefore, the high lux UV light may be irradiated only to a portion ofthe organic insulating material layer 152 corresponding to the secondbank 153b of FIG. 8D. Moreover, since the first bank 153a has the firstwidth wider than the width of the light-transmitting region TA of theexposing mask 191, the high lux UV light irradiated through thelight-transmitting region TA is incident on the first bank 153a and isnot incident on other areas after passing through the organic insulatingmaterial layer 152.

At this time, no UV light passes through the first bank 153a because thefirst bank 153 absorbs light and blocks penetration of light.

Accordingly, even though the high lux UV light is irradiated to theorganic insulating material layer 152 for forming the second bank 153bof FIG. 8D, the UV light does not reach the gate line, the data line 130and the power line of a metallic material reflecting light under theorganic insulating material layer 152 or the stage of the scan-typeexposure apparatus 195 on which the first substrate 110 is disposed, andthere is no light reflected by the above-mentioned elements.Furthermore, no light is incident on a bottom surface of the organicinsulating material layer 152 on the first electrode 150 in the pixelregion P after being reflected by the above-mentioned elements.

Next, as shown in FIG. 8D, the second bank 153b is formed on the firstbank 153a by developing and removing the organic insulating materiallayer 152 of FIG. 8C exposed to light. The second bank 153b has thesecond width smaller than the first width of the first bank 153a. Thesecond bank 153b is disposed on edges of the first bank 153a.

Here, the organic insulating material layer 152 of FIG. 8C contactingthe first electrode 150 is completely removed, and thus there is nohydrophobic residue on the first electrode 150. Therefore, the liquidphase organic light emitting material for forming the organic lightemitting layer 155 of FIG. 8H is spread well when it is sprayed ordropped.

Moreover, the second bank 153b does not have tails due to UV lightreflected perimetrically and has the second width, which issubstantially equal to the designed width.

In the meantime, the first bank 153a has a thickness thinner than thesecond bank 153b.

Next, as shown in FIG. 8E, after forming the bank 153 having thedouble-layered structure, an organic light emitting material layer 154is formed on the first electrode 150 and the first bank 153a exposedoutwards side surfaces of the second bank 153b by spraying or dropping aliquid phase organic light emitting material in a region surrounded bythe bank 153, more particularly, surrounded by the second bank 153b, inthe pixel region P with an liquid-releasing apparatus 199 or anozzle-coating apparatus (not shown).

Even if the organic light emitting material is sprayed or dropped on thesecond bank 153b because of a mis-alignment of the liquid-releasingapparatus 199 or the nozzle-coating apparatus, the organic lightemitting material is concentrated into a center of the pixel region Pbecause the second bank 153b has the hydrophobic property. In addition,even if an excessive amount of the organic light emitting material issprayed or dropped, the organic light emitting material does not flowover the second bank 153b due to the hydrophobic property of the secondbank 153b.

Moreover, since the hydrophobic residue does not exist on the firstelectrode 150, the liquid phase organic light emitting material isspread well on the first electrode 150. Furthermore, the organic lightemitting material layer 154 is formed on the first bank 153a because thesecond bank 153b has the second width smaller than the first bank 153a,and the organic light emitting material is concentrated into the centerof the pixel region P when it is sprayed or dropped. Thus, the thicknessof the organic light emitting material layer 154 is prevented from beingthickened around the second bank 153b.

Accordingly, the organic light emitting material layer 154 has a flattop surface and a uniform thickness without deviation in thickness inthe pixel region P surrounded by the first bank 153a. The pixel region Psurrounded by the first bank 153a corresponds to an effective lightemission area where an image is displayed to a viewer, and the effectivelight emission area is larger than that of the related art OLED displaydevice including the bank 53 of FIG. 1C. Therefore, the aperture ratiois increased.

Next, as shown in FIG. 8F, by performing a curing process, solvents andmoisture in the organic light emitting material layer 154 of FIG. 8E areremoved such that the organic light emitting layer 155 is formed in thepixel region P.

Here, the organic light emitting layer 155 has a single-layeredstructure. Alternatively, to improve light emission efficiency, theorganic light emitting layer 155 may have a multi-layered structure,which may be formed by the same method as that of the single-layeredstructure or may be formed in an entire surface of a display region by adeposition method. For example, the organic light emitting layer 155 mayinclude a hole injecting layer, a hole transporting layer, a lightemitting material layer, an electron transporting layer and an electroninjecting layer stacked on the first electrode 150 as an anode. Theorganic light emitting layer 155 may be a quadruple-layered structure ofthe hole transporting layer, the light emitting material layer, theelectron transporting layer and an electron injecting layer or atriple-layered structure of the hole transporting layer, the lightemitting material layer and the electron transporting layer.

Next, as shown in FIG. 8G, the second electrode 160 is formed on theorganic light emitting layer 155 by depositing a metallic materialhaving a relatively low work function. The second electrode 160 isformed on an entire surface of the display region. The metallic materialincludes at least one of Al, Al alloy such as AlNd, Ag, Mg, Au and AlMg.

As explained above, the first electrode 150, the organic light emittinglayer 155 and the second electrode 160 constitute the light emittingdiode E.

Next, as shown in FIG. 8H, after forming a seal pattern (not shown) onedges of the first substrate 110 or the second substrate 170, the firstand second substrates 110 and 170 are attached under a vacuum conditionor an inert gas condition such that the OLED display device isfabricated. Alternatively, a paste seal (not shown), which is formed ofa frit material, an organic insulating material or a polymer materialhaving transparent and adhesive properties is formed over an entiresurface of the first substrate 110, and then the first and secondsubstrates 110 and 170 are attached. As explained above, instead of thesecond substrate 170, an inorganic insulating film or an organicinsulating film may be used for an encapsulation and may be attached byan adhesive layer.

In the OLED display device of the invention, since the bank has thedouble-layered structure of the first bank blocking penetration of lightand having the first width and the second bank having the hydrophobicproperty and the second width smaller than the first width, thehydrophobic residues hardly remain on the first electrode even if thebank is formed using the scan-type exposure apparatus with high lux UVlight.

Therefore, the liquid phase organic light emitting material is spreadwell in the pixel region surrounded by the bank when it is sprayed ordropped.

Moreover, the organic light emitting layer has a uniform thickness inthe pixel region, and the organic light emitting layer is prevented frombeing degraded, thereby lengthening lifetime of the device.

Furthermore, the effective light emission area, where the organic lightemitting layer has the flat top surface, i.e., a uniform thickness, isincreased due to the second width of the second bank smaller than thefirst width. As a result, the aperture ratio of the OLED display deviceis improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An organic light emitting diode display device,comprising: a first substrate including a display region, wherein aplurality of pixel regions are defined in the display region; a firstelectrode over the first substrate and in each of the plurality of pixelregions; a first bank on edges of the first electrode and including aninsulating material having a property for blocking penetration of light;a second bank on the first bank and including an insulating materialhaving a hydrophobic property; an organic light emitting layer on thefirst electrode and a portion of the first bank surrounded by the secondbank in each of the plurality of pixel regions, wherein the organiclight emitting layer on the portion of the first bank directly contactsside surfaces of the second bank; and a second electrode on the organiclight emitting layer and covering an entire surface of the displayregion, wherein the first bank and the second bank form a double-layeredstructure, and the insulating material of the first bank is differentfrom the insulating material of the second bank.
 2. The organic lightemitting diode display device according to claim 1, wherein theinsulating material included in the first bank is a light-absorptionmaterial.
 3. The organic light emitting diode display device accordingto claim 1, wherein the first bank has a first width and the second bankhas a second width smaller than the first width.
 4. The organic lightemitting diode display device according to claim 1, wherein the firstbank includes chromium oxide CrOx, and the second bank includes at leastone of polyimide containing fluorine, styrene, methylmethacrylate, andpolytetrafluoroethylene.
 5. The organic light emitting diode displaydevice according to claim 1, further comprising: a switching thin filmtransistor and a driving thin film transistor in each of the pluralityof pixel regions and under the first electrode; and a passivation layercovering the switching thin film transistor and the driving thin filmtransistor and exposing a drain electrode of the driving thin filmtransistor, wherein the first electrode is disposed on the passivationlayer and contacts the drain electrode of the driving thin filmtransistor.
 6. The organic light emitting diode display device accordingto claim 5, further comprising: a gate line and a data line connected tothe switching thin film transistor and crossing each other to defineeach of the plurality of pixel regions; and a power line connected tothe driving thin film transistor and parallel to the gate line or thedata line.
 7. The organic light emitting diode display device accordingto claim 6, further comprising a second substrate facing the firstsubstrate or an encapsulation film contacting the second electrode.
 8. Amethod of fabricating an organic light emitting diode display device,comprising: forming a first electrode over a first substrate including adisplay region, which includes a plurality of pixel regions, the firstelectrode formed in each of the plurality of pixel regions; forming afirst bank on edges of the first electrode and including an insulatingmaterial blocking penetration of light; forming a second bank on thefirst bank, the second bank including an insulating material having ahydrophobic property; forming an organic light emitting layer on thefirst electrode and a portion of the first bank surrounded by the secondbank in each of the plurality of pixel regions, wherein the organiclight emitting layer on the portion of the first bank directly contactsside surfaces of the second bank; and forming a second electrode on theorganic light emitting layer, the second electrode covering an entiresurface of the display region, wherein the first bank and the secondbank form a double-layered structure, and the insulating material of thefirst bank is different from the insulating material of the second bank.9. The method according to claim 8, wherein the insulating materialincluded in the first bank is a light-absorption material.
 10. Themethod according to claim 8, wherein the first bank includes chromiumoxide CrOx, and the second bank includes at least one of polyimidecontaining fluorine, styrene, methylmethacrylate, andpolytetrafluoroethylene.
 11. The method according to claim 8, whereinthe first bank has a first width and the second bank has a second widthsmaller than the first width.
 12. The method according to claim 11,wherein forming the second bank includes: forming an organic insulatingmaterial layer on the first bank by applying the insulating materialhaving the hydrophobic property to an entire surface of the firstsubstrate; disposing an exposing mask including a light-transmittingregion and a light-blocking region over the organic insulating materiallayer and irradiating UV light of 100 to 990 mW/cm² to the organicinsulating material layer through the exposing mask; and developing theorganic insulating material layer, which has been exposed to the UVlight, wherein the light-transmitting region is disposed over anoverlapping area of the first bank and the second bank such that the UVlight is irradiated only to the overlapping area corresponding to thesecond width.
 13. The method according to claim 12, wherein forming theorganic light emitting layer includes: forming an organic light emittingmaterial layer on the first electrode and the portion of the first bankin each of the plurality of pixel regions surrounded by the second bankby spraying or dropping a liquid phase organic light emitting materialusing an liquid-releasing apparatus or a nozzle-coating apparatus; andcuring the organic light emitting material layer to form the organiclight emitting layer.
 14. The method according to claim 8, furthercomprising: forming gate and data lines and a power line and forming aswitching thin film transistor and a driving thin film transistor ineach of the plurality of pixel regions before forming the firstelectrode, the gate and data lines crossing each other to define each ofthe plurality of pixel regions, the power line parallel to the gate lineor the data line, the switching thin film transistor connected to thegate and data lines, and the driving thin film transistor connected tothe power line and the switching thin film transistor; and forming apassivation layer covering the switching thin film transistor and thedriving thin film transistor and exposing a drain electrode of thedriving thin film transistor, wherein the first electrode is disposed onthe passivation layer and contacts the drain electrode of the drivingthin film transistor.
 15. An organic light emitting diode display devicecomprising: a first substrate; a plurality of gate lines and a pluralityof data lines crossing each other to define a plurality of pixel regionsin a display region; a thin film transistor on the first substrate andin each of the plurality of pixel regions; a first electrode having afirst portion, second portion and third portion on the thin filmtransistor; a bank disposed on the second and third portions of thefirst electrode, the bank having a double-layered structure andincluding a first bank and a second bank on the first bank; an organiclight emitting layer having a central region with a first height and anedge region with a second height on the first portion of the firstelectrode, the first height of the organic light emitting layer and thesecond height of the organic light emitting layer are different; and asecond electrode on the organic light emitting layer, wherein thecentral region of the organic light emitting layer contacts with thefirst portion of the first electrode, and the edge region of the organiclight emitting layer on a portion of the first bank directly contacts aside surface of the second bank, and wherein the second bank includes aninsulating material having a hydrophobic property, and the first bankincludes a material different from the insulating material of the secondbank.
 16. The organic light emitting diode display device according toclaim 15, wherein the first height of the organic light emitting layeris less than the second height of the organic light emitting layer. 17.The organic light emitting diode display device according to claim 15,wherein a transition from the first height of the organic light emittinglayer to the second height of the organic light emitting layer is acurved slope.
 18. The organic light emitting diode display deviceaccording to claim 15, wherein a transition from the first height of theorganic light emitting layer to the second height of the organic lightemitting layer is a linear slope.
 19. The organic light emitting diodedisplay device according to claim 15, wherein the second portion of thefirst electrode is adjacent to an edge of the data line, and the thirdportion of the first electrode is connected to the thin film transistor.20. The organic light emitting diode display device according to claim15, wherein the thin film transistor includes a switching thin filmtransistor connected to one of the plurality of gate lines and one ofthe plurality of data lines and a driving thin film transistor connectedto the switching thin film transistor, and wherein the third portion ofthe first electrode is connected to the driving thin film transistor.21. The organic light emitting diode display device according to claim20, wherein each of the switching thin film transistor and the drivingthin film transistor includes a gate electrode, a semiconductor layer, asource electrode and a drain electrode.
 22. The organic light emittingdiode display device according to claim 21, wherein the semiconductorlayer includes one of oxide semiconductor, amorphous silicon, andpolysilicon.
 23. The organic light emitting diode display deviceaccording to claim 21, wherein each of the switching thin filmtransistor and the driving thin film transistor further includes anetch-stopper covering a center of the semiconductor layer, and whereinthe source and drain electrodes are spaced apart from each other on theetch-stopper.
 24. The organic light emitting diode display deviceaccording to claim 15, further comprising a passivation layer betweenthe thin film transistor and the first electrode and having a draincontact hole, wherein the third portion of the first electrode contactsa drain electrode of the thin film transistor through the drain contacthole, and the bank covers the drain contact hole.
 25. The organic lightemitting diode display device according to claim 24, wherein the draincontact hole overlaps a semiconductor layer of the thin film transistor.26. The organic light emitting diode display device according to claim24, further comprising an interlayer insulating layer between asemiconductor layer and the drain electrode and having a semiconductorcontact hole, wherein the drain electrode is connected to thesemiconductor layer through the semiconductor contact hole, and thedrain contact hole overlaps the semiconductor contact hole.
 27. Theorganic light emitting diode display device according to claim 15,wherein the bank includes a light blocking material.
 28. The organiclight emitting diode display device according to claim 15, wherein thefirst bank has a first width and the second bank has a second widthsmaller than the first width.
 29. The organic light emitting diodedisplay device according to claim 15, wherein there is no residue of thebank material between the organic light emitting layer and the firstportion of the first electrode.
 30. The organic light emitting diodedisplay device according to claim 15, further comprising a secondsubstrate facing the first substrate or an encapsulation film contactingthe second electrode.
 31. An organic light emitting diode display devicecomprising: a first substrate; a plurality of gate lines and a pluralityof data lines crossing the plurality of gate lines in a display region;a first electrode having a first portion, second portion and thirdportion; a bank disposed on the second and third portions of the firstelectrode, the bank having a double-layered structure and including afirst bank and a second bank on the first bank; an organic lightemitting layer having a central region with a first height and an edgeregion with a second height on the first portion of the first electrode,the first height of the organic light emitting layer and the secondheight of the organic light emitting layer are different; and a secondelectrode on the organic light emitting layer, wherein the centralregion of the organic light emitting layer contacts with the firstportion of the first electrode, and the edge region of the organic lightemitting layer on a portion of the first bank directly contacts a sidesurface of the second bank, and wherein the second bank includes aninsulating material having a hydrophobic property, and the first bankincludes a material different from the insulating material of the secondbank.
 32. The organic light emitting diode display device according toclaim 31, wherein the first height of the organic light emitting layeris less than the second height of the organic light emitting layer. 33.The organic light emitting diode display device according to claim 31,wherein a transition from the first height of the organic light emittinglayer to the second height of the organic light emitting layer is acurved slope.
 34. The organic light emitting diode display deviceaccording to claim 31, wherein a transition from the first height of theorganic light emitting layer to the second height of the organic lightemitting layer is a linear slope.